Justification:Global: This formerly widespread and abundant large oceanic shark is subject to fishing pressure virtually throughout its range. It is caught in large numbers as a bycatch in pelagic fisheries, with pelagic longlines, probably pelagic gillnets, handlines and occasionally pelagic and even bottom trawls. Catches, particularly in international waters, are inadequately monitored. Its large fins are highly prized in international trade although the carcass is often discarded. Fishery pressure is likely to persist if not increase in future. Outside of the areas detailed below, this species is under similar fishing pressure from multiple pelagic fisheries, there are no data to suggest that declines would and have not have also occurred in these areas, given there are similar fisheries throughout the range. As such, a precautionary global assessment of Vulnerable is considered appropriate for the oceanic whitetip. Efforts are underway to improve the collection of data from some regions and effective conservation and management of this species will require international agreements.

Northwest Atlantic and Western Central Atlantic: The oceanic whitetip shark is assessed as Critically Endangered in the Northwest and Western Central Atlantic because of the enormous declines that have been reported. Two estimates of trends in abundance from standardized catch rate indices were made from independent datasets. An analysis of the US pelagic longline logbook data between 1992 and 2000, which covers the Northwest and Western Central Atlantic regions, estimated declines of 70%. An analysis of the Gulf of Mexico, which used data from US pelagic longline surveys in the mid-1950s and US pelagic longline observer data in the late-1990s, estimated a decline of 99.3% over this forty year time period or 98% over three generations (30 years). However, changes in fishing gear and practices over this time period were not fully taken into account in the latter analysis, and there is currently debate as to whether or not these changes may have resulted in an under- or overestimation of the magnitude of these declines.

This species, together with the silky shark Carcharhinus falciformis and blue shark Prionace glauca, has often been described as one of the three most abundant species of oceanic sharks and large marine animals (Compagno 1984, Taniuchi 1990, Bonfil 1994, Castro et al. 1999). Recent observations, however, indicate that this species that was formerly "nearly ubiquitous in water deeper than 180 m and above 20°C" (Castro et al. 1999) is now only occasionally recorded (e.g., Baum and Myers 2004, Domingo 2004).

The population dynamics and structure of this species are unknown. Distribution appears to depend on size and sex and the nursery areas appear to be oceanic (Seki et al. 1998). Larger individuals are caught deeper than smaller ones and there is geographic and sexual segregation (Anderson and Ahmed 1993). Longline catches in the Central Pacific show that this species definitely increases in abundance as a function of increasing distance from land, and, unlike the silky shark Carcharhinus falcifomis, it does not congregate around land masses (Compagno in prep.).

In the Northwest and Western Central Atlantic enormous declines are estimated to have occurred. Two estimates of trends in abundance from standardized catch rate indices have been made from independent datasets. An analysis of the US pelagic longline logbook data between 1992 and 2000, which covers the Northwest and Western Central Atlantic regions, estimated declines of 70% (Baum et al. 2003). An analysis of the Gulf of Mexico, which used data from US pelagic longline surveys in the mid-1950s and US pelagic longline observer data in the late-1990s, estimated a decline of 99.3% over this forty year time period (Baum and Myers 2004). When trends in abundance from the former analysis are extrapolated back to the mid-1950s, they match the latter analysis almost exactly (99.8%). Over a period of three generations (30 years), the estimated decline is 98%. However, the latter study has recently been criticized because temporal changes in fishing gear and practices over the time period were not taken fully into account and the study may, therefore, have exaggerated or underestimated the magnitude of the declines (Burgess et al. 2005, Baum et al. 2005).

This is one of the most widespread sharks, ranging across entire oceans in tropical and subtropical waters. The oceanic whitetip is an oceanic-epipelagic shark, usually found far offshore in the open sea in waters 200 m deep, between about 30°N and 35°S in all oceans; it is normally found in surface waters, although it has been recorded to 152 m. It has occasionally been recorded inshore, but is more typically found offshore or around oceanic islands and areas with narrow continental shelves (Fourmanoir 1961, Compagno in prep, Last and Stevens 1994). Temperatures of waters in which it regularly occurs are 18 to 28°C, with water above 20°C preferred. Although one whitetip was caught in water of 15°C it tends to withdraw from waters that are cooling below this, as in the Gulf of Mexico in winter (Compagno in prep.).

This is a slow-moving but quite active shark, apparently equally active at daytime or night (Compagno in prep., Ebert 2003).

Development is viviparous and embryos have a yolk sac placenta that attaches to the uterine wall of the mother (Bigelow and Schroeder 1948). Born at about 60 to 65 cm TL after a gestation period of about 10 to 12 months (Compagno in prep.), males mature at about 170 to 96 cm and females at 170 to 190 cm TL (Seki et al. 1998). Oceanic whitetip sharks grow to a large size, with some individual reaching almost 4 m. However, most known specimens are et al. 1973, Stevens 1984, Seki et al. 1998), although 15 foetuses were recorded from a female of 245 cm TL from the Red Sea (Gohar and Mazure 1964) and larger females appear to carry more young, although there may be regional variation (Bass et al. 1973). Birth is thought to occur in early summer in the northwest Atlantic and south west Indian Oceans (Bass et al. 1973), and January to March off New South Wales (Stevens 1984), whereas Seki et al. (1998) found that parturition was February to July in the North Pacific. Pregnant females of this species are less frequently found in the Indian Ocean than other sharks of this genus (Gubanov 1978). In the Central Pacific, females with small embryos have been found throughout the year, suggesting a less tight seasonality of birth (and presumably mating) than the Western Atlantic (Compagno in prep). Also, non-breeding adult females have been found to outnumber gravid females in the equatorial Central Pacific (Compagno in prep). The location of nurseries has not been reported, but very young oceanic whitetip sharks have been found well offshore along the southeastern US, suggesting offshore nurseries over the continental shelves (Compagno in prep).

Seki et al. (1998) studied the age, growth and reproduction of the oceanic whitetip in the north Pacific. They found similar growth rates in both males and females with a Von Bertalanffy equation of: Lt = 299.58 * {1 - e-0.103 x (t + 2.698)} where Lt is expressed as precaudal length in cm at age t. They used Bass et al.'s (1973) transformation of TL = 1.397 x PL for conversions to total length. Using vertebral analysis they showed that annular formation occurred in spring. Both male and female oceanic whitetips matured at 4 to 5 years of age. Smith et al. (1998) investigated the intrinsic rebound potential of Pacific sharks and found that oceanic whitetips to be among a moderate rebound potential, because of their relatively fast growth and early maturation.

Oceanic whitetip sharks have been caught in large numbers virtually everywhere they occur, particularly in pelagic longline and drift net fisheries. This species was initially described as the most common pelagic shark beyond the continental shelf in the Gulf of Mexico (Wathne 1959, Bullis 1961), and throughout the warm-temperate and tropical waters of the Atlantic and Pacific (Mather and Day 1954, Strasburg 1957). In the Gulf of Mexico, for example, between 2 and 25 of these sharks were usually observed following the vessel during longline retrieval on the exploratory surveys in the 1950s and their abundance was considered as a serious problem because of the high proportion of tunas they damaged (Bullis and Captiva 1955, Backus et al. 1956, Wathne 1959). Recent shark papers on the Gulf of Mexico have either not mentioned this species or have dismissed it as rare, not recognising its former prevalence in the area (Baum and Myers 2004).

Few data are available on the catch rate of these sharks, and this is a serious hindrance to assessing the status of this species in regions other than the Northwest Atlantic and Eastern Central Pacific. Strasburg (1958) reported that the oceanic whitetip shark constituted 28% of the total shark catch in exploratory tuna longline fishing south of 100 N latitude in the central Pacific Ocean. According to Berkeley and Campos (1988), oceanic whitetip sharks constituted 2.1% of the shark bycatch in the swordfish fishery along the east coast of Florida in 1981 to 1983. Taniuchi (1990) analysed Japanese fishery statistics and noted that this species was most commonly taken by fishery boats in the Pacific, where they made up 20 to 30% of the number of sharks taken by tuna longliners, compared to about 3 to 4% in the Indian Ocean, because the boats are fishing for southern bluefin tuna in cooler waters. Guitart Manday (1975) demonstrated a marked decline in the oceanic whitetip shark landings in Cuba from 1971 to 1973. In the Maldives, Anderson and Ahmed (1993) reported that oceanic whitetip sharks were taken commercially by pelagic shark longliners and incidentally by tuna fishermen, and that in a previous exploratory fishing survey oceanic whitetip sharks constituted 23% of all sharks caught.

Domingo (2004) reported that the Uruguayan longline fleet observer programme in 1998 to 2003 recorded catch rates of only 0.006 sharks/1,000 hooks in Uruguayan and adjacent high seas South Atlantic waters (latitude 26° to 37°, 16 to 23°C) and 0.09 sharks/1,000 hooks in international waters off the Atlantic coast of Africa. He notes that similarly infrequent records are obtained by Brazilian and Ecuadorian Atlantic longline fleets.

Conservation and management action are urgently required for this species; the only known conservation measure at present is a broad, multi-species pelagic shark quota for U.S. Atlantic waters. Specifically, fishing pressure on this species must be considerably decreased through reduction in fishing effort, catch limits, measures to enhance chances of survival after capture and possibly also through the implementation of large-scale oceanic non-fishing areas. Effective conservation of this species will require international cooperation. The oceanic whitetip is listed as a highly migratory species under the 1995 UN Agreement on the Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks (UNFSA). The Agreement specifically requires coastal States and fishing States to cooperate and adopt measures to ensure the conservation of these listed species. To date, there is little progress in this regard. See United Nations Convention on the Law of the Sea for further details. Also of relevance is the FAO International Plan of Action for the Conservation and Management of Sharks (IPOA-Sharks) which specifically recommends that Regional Fisheries Organisations (RFO) carry out regular shark population assessments and that member States cooperate on joint and regional shark management plans. This is of particular importance for pelagic sharks such as C. longimanus whose stocks are exploited by more than one State on the high seas. Although steps are being taken by some RFOs to collect species-specific data on pelagic sharks, and to ban the practise of shark finning, to date no RFO has limited shark catches or drafted a "Shark Plan" as suggested in the IPOA-Shark guidelines (R. Cavanagh, pers. comm).

Castro, J.I. 1983. The sharks of North American waters. Texas A & M University Press, College Station.

Compagno, L.J.V. 1984. FAO species catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. FAO Fisheries Synopsis No. 125, Volume 4, Part 1.

Compagno, L.J.V. In prep. b. Sharks of the World. An annotated and illustrated catalogue of the shark species known to date. Volume 3. (Carcharhiniformes). FAO Species Catalogue for Fisheries Purposes No. 1, Vol.3. FAO, Rome.

Taniuchi, T. 1990. The role of elasmobranchs in Japanese fisheries. In: H.L. Pratt Jr., S.H. Gruber and T. Taniuchi (eds). Elasmobranchs as living resources: advances in the biology, ecology, systematics, and the status of the fisheries. NOAA Technical Report NMFS 90: 415–426.